The present disclosure relates to a coating device and a corresponding coating method, for example for the painting of motor vehicle body parts.
Rotary atomizers may generally be driven pneumatically by means of an air turbine and atomise the paint to be applied by means of a bell cup which is rotating at high speed, and are conventionally used for painting motor vehicle body parts or other components. It is furthermore known to form the spray jet applied by the bell cup by means of so-called shaping air. To this end, shaping air nozzles are attached in the rotary atomizer axially behind the bell cup, which output a shaping air jet essentially in the axial direction from behind onto the spray jet, so that the opening angle of the spray jet can be influenced by the shaping air jet.
What is problematic in the use of shaping air is the fact that the shaping air supplied under pressure cools down suddenly when leaving the shaping air nozzle, which can lead to the disruptive formation of condensation water.
To solve this problem, JP 08 108 104 A proposed to preheat the supplied shaping air by means of electric heating and temperature regulation to a certain temperature, so that the temperature drop of the shaping air when leaving the shaping air nozzles is no longer sufficient to cause the disruptive formation of condensation water.
In addition to the previously described rotary atomizers with a pneumatic drive by means of a air turbine, rotary atomizers are for example also known from WO 2005/110619 A1, in the case of which the bell cup is driven by an electric motor. Here, the shaping air can also be used for cooling the electric motor, in that the shaping air is conveyed through the stator of the electric motor and in this case absorbs part of the electric waste heat arising in the stator and dissipates it.
In the case of the known rotary atomizers, the shaping air is thermally influenced during the passage through the rotary atomizer, that is to say in dependence on the operating state of the rotary atomizer, so that the shaping air temperature at the outlet of the shaping air nozzle fluctuates in dependence on the operating state of the rotary atomizer, which has a negative effect on the painting process, as the applied paint arrives on the component to be painted dryer or wetter, depending on the fluctuation of the shaping air temperature.
Although a coating device with a temperature-control device and a control unit is known from DE 102 39 517 A1, the heating device in this case does not heat the shaping air, but rather the drive air which is used to drive the air turbine. Furthermore, it is only mentioned in general in this published document that shaping air can be heated in order to prevent a cooling down of the components due to the decompression of the drive air of the turbine.
Although EP 1 688 185 A1 discloses a coating device with a shaping air nozzle and a temperature-control device as well as a control unit, the control unit in this case has a completely different function, as the shaping air temperature is not kept constant in this case, but rather is varied in a targeted manner.
Finally, WO 88/00675 A1 only discloses a temperature-control device for flowable masses in general. A temperature control of the shaping air is not known from this citation, however.
Accordingly, known rotary atomizers fail to provide for targeted temperature control of shaping air, resulting in a degradation of painting quality associated with the known rotary atomizers and corresponding operating methods atomizer. Thus, there is a need for an improved atomizer and method of operating an atomizer that provides improved temperature control of shaping air.